Enjoying the Summer

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Greetings to all RVing residents and visitors to the Great Northwest! It is our hope this finds you happy, healthy and on the road enjoying the RVing way of life! Summer is just beginning and many of us are certainly engaging in the expression of freedom that RVing brings, so as summer begins to heat up it’s time to turn our attention to the RV heating system. What? It will soon be 80-plus-degrees outside and you want to talk about furnaces? However odd that sounds, now is the time to prepare the RV furnace for the upcoming fall and winter seasons. Too often we wait until that first chilly night appears and then wonder why the furnace will not operate properly. The time to prepare your furnace is now, during the summer!

Though many aspects of servicing an RV furnace requires the expertise of a professional service tech, from a user’s standpoint, there are several tasks the average RV handyperson can perform that are advantageous to preserving the integrity of the heating system. The four key areas you should consider are:

•    Cleanliness
•    Voltage
•    Ducting
•    Return Air

A clean furnace is a happy furnace. As air moves in, out and around the furnace, dust, lint and other pollutants in the air will naturally accumulate. Too much accumulation and operational failure is all but guaranteed. Each RV furnace is typically equipped with two blower wheels or squirrel cages; one to bring in fresh air to mix with the propane, and one to “force” the air over the heated chamber and push it through the coach ducting to the interior living sections. Excess dirt and lint will eventually wedge inside the blower assembly, essentially weighing it down.

CleanlinessIn a normal sequence, the spinning of the main blower wheel closes a device called a sail switch. Even though adjusting the wall thermostat actually initiates the heating cycle, it’s the closing of the sail switch that starts the internal sequence of furnace operation. If the blower wheel is weighted down with excess dust and lint, (see photo), it will not spin fast enough to close the sail switch. Too much weight, the slower the spin; the slower the spin, the sail switch does not close. An open sail switch; the furnace fails to ignite.

Here’s where to start: With the thermostat in the off position, the propane container service valve completely off and the furnace at room temperature, vacuum in, around and about the innards of the furnace. It will likely be necessary to remove a front cover or access panel to expose the main furnace assembly. The goal is to keep the insides of the furnace assembly as clean as possible. Wipe all surfaces down with a damp shop rag.

Where the circuit board is easily accessible, take the time to clean the board contacts. At a minimum, use a pencil eraser to brighten the contact strip, or better yet, use an electrical cleaner/preservative to chemically remove oxides from the contacts.

WarmAirDuctCleanliness of the warm air ducting is also crucial. Regardless of the type of delivery ducting in your rig, remove each register and vacuum as far into each duct as possible. The duct in this photo, discovered during an annually cleaning procedure, turned out to be the perfect location for mice to nest!


VentsOn the exterior of the RV, inspect the intake and exhaust vents carefully. If the coach has been inactive for a period of time, it’s common to find mud daubers or wasp’s nests inside the cozy confines of the vent tubes. Blockages in the intake tube can result in an overly rich fuel mixture, creating operational faults. Blockages in the exhaust tube can result in overheating, short cycling of the furnace and pose a fire hazard.

Probably the number one cause of flawed heating cycles in forced air systems today is low battery voltage. Furnace fan motors can create a relatively large amp draw on a malnourished battery bank. Add the excess weight of filthy blower wheels and current usage ramps even higher.

The minimum voltage requirement for most all 12-volt DC forced air furnaces is 10.5-volts DC, measured at the furnace. Conversely, excessively higher than normal DC voltages (above 13.5-volts DC), can create their own palette of problems for the delicate components found on some circuit boards. Maintaining a properly charged battery bank is critical for optimum furnace operation.

Aside from the cleanliness issue mentioned above, for those coach owners with individual runs of 4-inch flexible ducts, inspect and straighten all sharp bends or turns whenever possible. Shorten any lengths that appear too long. Excess duct lengths can create an overheated situation within the furnace housing and prohibit sufficient hot air delivery throughout the living sections.

Return Air
A clear path of return air to the furnace enclosure is nothing short of a mandate. A literal “breathing” appliance, the forced air furnace must also inhale fresh breaths of return air as the warm air is circulated throughout the RV in order to operate optimally. You’ve likely seen at least one interior vent located near the furnace compartment, such as in this photo of one under a dinette seat. This is the pathway of return air back to the furnace compartment.

FilternonoSome coach owners mistakenly install a filter in this vent space; a definite no-no. Unlike a home heating appliance, there should not be a filter installed anywhere in the path of the return air. Additionally, never stow gear or supplies in the furnace compartment. Aside from a fire hazard, it may inhibit the path of return air.

Keep the above four Key Factors in mind and in practice prior to that first frost and you too can enjoy many years of warmth from your RV heating system. Remember, RVing is more than a hobby, it’s a lifestyle!

Gary Bunzer is popularly known as The RV Doctor and has a wealth of experise and experience with the technical aspects of RVing. He is a popular seminar speaker at the Seattle and Puyallup RV Shows as well as national shows across the country.

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